1. Technical Field
The inventive concept relates to a nonvolatile memory device and a method of manufacturing the same, and more particularly, to a phase-change random access memory (PCRAM) device and a method of manufacturing the same.
2. Related Art
A lot of effort has been placed in realizing nonvolatile memory devices, such as PCRAMs, having a multi-level structure, while minimizing changes in a memory cell structure.
As part of this effort, technology for realizing the multi-levels by changing a degree of phase-change in a phase-change material by supplying a write voltage to a bit line of the PCRAMs step-by-step, has been suggested.
However, it is difficult to read out an accurate value in the PCRAM when the write voltage has been supplied step-by-step, as described above.
That is, in a high-integration PCRAM, adjacent memory cells, particularly cells connected to the same bit line, are formed close to one another. Thus, these cells are vulnerable to disturbance from a adjacent memory cells. Even when the write voltage is supplied step-by-step, a desired phase-change is not caused due to an effect of the adjacent memory cells. Thus, it is difficult to verify the memory cells and to realize a multi-level structure.